INTRODUCTION

In France and in French-speaking Switzerland, research on intelligence has traditionally referred to a relatively wide range of studies. On the one hand, intelligence is studied by differentialists – differential psychology, in the Francophone tradition, refers to both psychometrics and to the study of individual differences, the latter referring both to fundamental and to applied issues – who devise and use tests of intelligence. On the other hand, because Piaget referred to the “development of intelligence,” it also includes developmental studies of cognition, in particular, the Piagetian studies. Currently, researchers working in the Piagetian tradition no longer consider that they work on intelligence, but this is a relatively recent shift. Thus, the study of intelligence is not restricted to the use of standardized tests of intelligence scales nor to interest in individual differences. For example, the Traité de Psychologie Expérimentale, first edited in 1963, devoted a whole volume to the study of intelligence (Oléron et al., 1963), three chapters of which consisted essentially of the presentation of the Piagetian theory by Piaget and collaborators. As in many other countries, experimental psychologists working with adults on reasoning, problem solving, language, or other cognitive functions do not consider that they are working on intelligence.

This chapter therefore reflects these fuzzy frontiers including the differential and the Piagetian traditions but not the other types of cognitive studies.